1. Field of the Invention
The present invention relates to a work vehicle, more particularly to an attachment construction for attaching a boom of a front loader to a front of a traveling vehicle such as a tractor. The invention relates also to the work vehicle having this attachment construction.
2. Description of the Related Art
Conventionally, there is known a work vehicle comprising a tractor as an example of a traveling vehicle and a front loader mounted to the front of the tractor for use in carrying of a load, and loading/unloading operation thereof.
The vehicle body of the tractor comprises an assembly of a clutch housing, a transmission case, a differential case etc. connected in series and disposed rearwardly of an engine. The tractor includes a front axle frame fixedly attached to and projecting from the opposed sides of the engine.
The front loader includes a pair of support tables projecting from the front portion of the tractor body to the right and left outer sides thereof, a pair of boom supports disposed erect on the right and left support tables, a pair of booms pivotally connected to the tops of the right and left boom supports to be pivotable about a right/left axis, and a bucket attached to the leading ends of the right and left booms. The respective booms are vertically pivotable by means of boom cylinders interposed between the respective booms and the boom supports, and the bucket is pivotally operated by means of boom cylinders interposed between the bucket and the respective booms.
In some known front loaders, to cope with a load applied from the bucket in the course of a loader operation, to the end of reinforcement, there are provided braces extending forwardly and downwardly from the boom supports and connected to the front axle frame or connectors interconnecting the right and left boom supports to each other. In such constructions having the braces or connectors, the presence of these braces or connectors can interfere with a maintenance operation of the inside of an engine hood and/or interfere with the tractor operator's field of front vision.
In order to avoid this inconvenience, the prior art has proposed a work vehicle designed to achieve the maintenance readiness and operator's visibility by elimination of the braces or connectors (see JP-A-2003-278176).
In this work vehicle, an attaching bracket made of plate members is fixedly welded to right/left inner sides of the support tables, with a portion of the attaching bracket being bolt-fixed to the clutch housing and a front attaching portion of the attachment bracket extending from the support tables being bolt-fixed to the front axle frame.
Further, a bracket projects from each boom support and a front end portion of a sub frame disposed on each side of the vehicle body is superposed on the lateral face of the bracket and this bracket and the front end portion of the sub frame are fixed by means of a bolt and a nut having a transverse axis and a rear end portion of the sub frame is connected to a rear portion of the vehicle body.
With the above-described conventional work vehicle, the front end of the sub frame is superposed on and bolt-fixed to the lateral face of the bracket which projects downwardly from the boom support. Since the sub frame and the bracket can move, though very slightly, in the fore and aft direction relative to each other, when a load is applied from the boom via the boom support to the support table, this load is applied mainly to the attached portion of the support table relative to the vehicle body during a loader operation.
And, the arrangement that the attaching bracket for attaching the support table to the vehicle body projects forwardly is not sufficient by itself to effectively distribute the load applied from the boom to the attached portion of the support table to the vehicle during a loader operation. As a result, a significant load will be applied to the vehicle body, thus resulting in premature damage of the clutch housing.
Incidentally, in the case of the conventional work vehicle, the front portion of the sub frame is attached to the side of the boom support. Hence, when the support table, the boom support, etc. are dismounted from the vehicle body, the sub frame too will be detached therefrom. Therefore, the sub frame does not serve as a reinforcing member for the vehicle body.
In view of the above-described state of the art, a primary object of the present invention is to provide an attachment construction for a front loader which construction achieves effective distribution of a load applied to an attached portion of a support table attached to a vehicle body during a loader operation and also to provide a work vehicle having such attachment construction.